This section is from the book "A Text-Book Of Pharmacology, Therapeutics And Materia Medica", by T. Lauder Brunton. Also available from Amazon: A text-book of pharmacology, therapeutics and materia medica.
Extract of Socotrine aloes, 120 gr.; myrrh, 90 gr.; saffron, 90 gr.; carbonate of potassium, 60 gr.; extract of liquorice, 1 oz.; compound tincture of cardamoms, 8 fl. oz.; distilled water up to 30 fl. oz.
B.P. Extractum Aloes Socotrinae. Treating with boiling water, separating insoluble matter by subsidence and filtration, and evaporating the clear solution.
B.P. Tinctura Aloes. Tincture of Aloes. - Socotrine aloes, 1/2 oz.; extract of liquorice, 1 1/2 oz.; proof spirit, to 20 fl. oz.
U.S.P. Extractum Aloes Aquosum. Aqueous Extract of Aloes. - Aloes, 100; boiling distilled water, 1,000. Separate the insoluble matter by subsidence and filtration, and evaporate.
Composition. - All kinds of aloes contain a bitter substance, aloin, to which their activity is due. It has in each kind of aloes a slightly different composition, and has received a name showing its source - socaloin from Socotrine aloes, barbaloin from Barbadoes aloes, and nataloin from Natal aloes. According to some authors these substances are isomeric; according to others they form a homologous series. Besides aloin, aloes contains resinous substances and traces of an ethereal oil.
Barbaloin and nataloin are distinguished from socaloin by giving with a drop of nitric acid, on a porcelain slab, a bright crimson colour. With barbaloin this gradually fades, but it is permanent with nataloin. Socaloin does not give this reaction. Barbaloin is distinguished from nataloin by the latter giving a fine blue colour, while the former remains unchanged, on adding a minute quantity of each to one or two drops of strong sulphuric acid and then bringing a glass rod dipped in nitric acid so near that the vapour shall pass over the surface.